Three cheers for the Los Angeles Times and its investigative reporting about the impact of teacher quality:

Seeking to shed light on the problem, The Times obtained seven years of math and English test scores from the Los Angeles Unified School District and used the information to estimate the effectiveness of L.A. teachers — something the district could do but has not. The Times used a statistical approach known as value-added analysis, which rates teachers based on their students’ progress on standardized tests from year to year. Each student’s performance is compared with his or her own in past years, which largely controls for outside influences often blamed for academic failure: poverty, prior learning and other factors.

The paper found that not every teacher is a good teacher and the quality of a teacher has a dramatic impact on students’ learning, or lack thereof. The unions, of course, are livid.

The Los Angeles teachers union president said Sunday he was organizing a “massive boycott” of The Times after the newspaper began publishing a series of articles that uses student test scores to estimate the effectiveness of district teachers. “You’re leading people in a dangerous direction, making it seem like you can judge the quality of a teacher by … a test,” said A.J. Duffy, president of United Teachers Los Angeles, which has more than 40,000 members.

Apparently, Duffy thinks it a great sin to judge teachers by how much their students learn from them in the classroom. What’s next, judging the quality of firefighters by their ability to put out fires?